Intrathecal dexmedetomidine can decrease the 95% effective dose of bupivacaine in spinal anesthesia for cesarean section: A prospective, double-blinded, randomized study.

Background: Dexmedetomidine (Dex), as an adjuvant, has been reported to prolong the duration of spinal analgesia when adding to local anesthetic. We hypothesized that Dex could enhance the efficiency of intrathecal bupivacaine for spinal anesthesia in cesarean section. The aim of his study is to test our hypothesis that 5 μg Dex could enhance the efficiency of intrathecal bupivacaine and reduce the dose requirement of spinal bupivacaine for patients undergoing cesarean section.
Methods: Ninety patients with ASA I or II, who underwent cesarean section, were randomized into 2 groups: group D (bupivacaine + 5 μg Dex) and group C (bupivacaine + the same volume of saline). The subsequent dose of spinal bupivacaine was determined by the improved up-down allocation method. The initial dose of bupivacaine in the 2 groups was 4 mg, and the subsequent dose for the following patient was depended on the probability of the current dose. ED95 of spinal bupivacaine was calculated using logistic regression model.
Results: The ED95 and 95% confidence intervals (95% CI) of spinal hyperbaric bupivacaine in group D and group C were 7.4 mg (95% CI, 5.6-12.4 mg) and 11.0 mg (95% CI, 4.4-56.8 mg), respectively. The duration of sensory block was 120.5 ± 37.0 minutes in Dex group and 70.5 ± 34.5 minutes in Control group, respectively (P < .05). The duration of analgesia was 230.5 ± 40.5 minutes in Dex group and 145.1 ± 28.5 minutes in Control group, respectively (P < .001). The consumption of postoperative rescued sufentanil was significantly lower in Dex group than in the Control group (56.3 ± 9.4 vs 65.9 ± 10.7 μg). There was not significantly different in the patient satisfaction of analgesia, incidence of side effects, neonatal outcomes and neurological deficit between the 2 groups.
Conclusion: Intrathecal 5 μg Dex enhances the efficacy of spinal bupivacaine by 24% in patients undergoing cesarean section with spinal anesthesia. No additional side effect was observed by adding spinal Dex.